I have a sorted array of numbers:

```
A = [1, 4, 10, 15, 18]
```

I want to determine the first index where a value, `v`

, occurs in this array (or 0 if it does not occur), like `findfirst(A, v)`

. But I want to exploit the fact that `A`

is already sorted (binary search). Is this already implemented in Julia? I did not find anything on the docs for `findfirst`

.